I had this problem with a Torx 5 screw inside a MacBook Air, tried every trick in the book to get the !@#$ thing out, to no avail. Here's what ended up working for me:
I very carefully sanded the surface of the stripped screw with 320 grit sandpaper, making extra sure I wasn't contacting any surrounding components. Then I cleaned the screw head off and applied some petroleum based soldering flux onto the sanded screw head. I then got my soldering iron up to temperature and melted some solder onto the head of the screw. I added solder until it filled the stripped out torx hole and formed a small dome on top of the screw. While the solder was still melted, I pressed a flathead screwdriver into the solder and kept it still until the solder cooled. When I removed the screwdriver tip, there was a perfect flathead impression in the solder. Then I just used the flathead screwdriver to remove the screw normally...it came right out! I suggest anyone who has the parts/supplies to do this, definitely give it a try.